Relations among interaural cross-correlation coefficient (IACCE), lateral fraction (LFE), and apparent source width (ASW) in concert halls

Relations are determined between one of the important subjective attributes of concert hall acoustics, the apparent source width, ASW, and three acoustical measures, interaural cross-correlation coefficient IACCE, LFE, and strength factor G. Although these measures previously have been found to correlate with ASW, their relations with it have not been examined sufficiently, especially in respect to their frequency characteristics. Herein, ASW's are directly determined for electronically reproduced musical sound fields with extensive ranges of values for IACCE and LFE. Investigated as parameters are angles of incidence, the time delay difference between a pair of symmetric early lateral reflections, and the number of early lateral reflections. These studies indicate the relative efficacy of IACCE and LFE for determining ASW under conditions that are realistically encountered in concert halls. The results were compared with measured IACCE's, LFE's, and also the strength factor G's in existing concert halls. It is concluded that the arithmetic average of 1-IACCE's at 500, 1 k and 2 k Hz combined with the strength factor Glow of the sound field at frequencies below 250 Hz are physical measures highly correlated with the subjective rank ordering of concert halls and that they cover the effects on ASW of the entire octave-band frequency range from 125 to 4 k Hz.